1. Field of the Invention
This invention relates to a connector usable in, for example, medical instruments, such as ultrasonic diagnostic equipment, semiconductor testing equipment, computers, and industrial equipment with a multicore electric input/output section, such as communications equipment.
2. Description of the Related Art
More particularly, this invention relates to a multicore connector with a plug and a receptacle used for an electrical connection between electronic apparatuses utilizing a multi-core cable or the like.
Sophisticated electronic apparatuses, including medical instruments, semiconductor testing equipment, computers, and communications equipment, have been getting smaller in size and more sophisticated. In addition, the signals they have to transmit and receive have become more diversified and complex. Thus, the input/output and transmission/reception cables of a plurality of electronic apparatuses connected to one another tend to have more cores, which thus requires multicore connectors smaller in size, higher in density, and of higher reliability.
Multicore connectors involve connection of many contact parts. When a plug and a receptacle are connected to each other, and when the plug is pulled out of the receptacle, it is desirable that the insertion force and the pulling force be very small. Furthermore, there have been demands for long-service-life connectors with less wear of the contact parts.
FIG. 11 shows an example of a conventional multicore connector 100. The multicore connector 100 is composed of a plug 101, connected to one (not shown) electronic apparatus, and a receptacle 102, connected to another (not shown) apparatus. When they are connected to each other, after the plug 101 is inserted into the receptacle 102 (with zero insertion force) and joined with each other, a handle 103 is turned, thereby rotating a cam shaft 104 provided on the plug central part.
By this process, the action of a cam 105 provided in the lower part of the cam shaft 104 slides an actuator 106 in the lateral direction, thereby moving a contact 108 formed at the tip of a contact pin 107 to a contact 109 of the receptacle 102 in such a manner that the contact 108 comes into contact with the contact 109. Each contact pin is displaced elastically, causing the contact 108 of the plug 101 to press against the corresponding contact 109 of the receptacle 102, which connects the plug and receptacle to each other electrically. The rotation of the cam shaft 104 sets a lock between the plug 101 and the receptacle 102, which secures the plug 101 to the receptacle 102 reliably.
For instance, in an ultrasonic apparatus, when this type of connector is used to connect the signal cable of the ultrasonic sensor to the apparatus body, the following approach is used: the receptacle 102 is fixed to the circuit board (not shown) in the ultrasonic apparatus and each contact terminal 110 is soldered to the corresponding wire on the circuit board, and the plug 101 is engaged with the receptacle 102, thereby making an electrical connection. To wire the plug with a multicore cable, the cores of the multicore cable (not shown) are contact-bonded or soldered to contact terminals 111. Alternatively, the contact terminals are mounted on a specific circuit board. Then, a cable is drawn out of the wiring of the circuit board. However, in the conventional multicore connector of FIG. 11, the contacts 108 and 109 are long, which permits crosstalk or a similar problem to occur between the contacts, depending on usage.
FIG. 12 shows a conventional example of a multicore connector 200 developed to solve the crosstalk problem or the like. The multicore connector 200 is also composed of a plug 201 and a receptacle 202 as the connector of FIG. 11. FIG. 12 shows a state where the plug 201 and the receptacle 202 are connected to each other electrically in the conventional example.
The plug 201 has a plug housing 203. In the lower part of the housing 203, there is provided a plug board 204 composed of a multilayer wiring insulating board. On the top surface of the plug board 204, a plurality of electrode pads 205 are formed which are to be connected to the individual cores (not shown) of the multicore cable extending from one electronic apparatus to be connected. A plurality of contact pads 206 corresponding to the electrode pads 205 are formed on the bottom surface of the plug substrate 204, which connects the contact pads 206 corresponding to the electrode pads 205 to the electrode pads 205 electrically inside the plug board 204. The plug 201 further has a cam shaft 207 provided rotatably in the central part of the plug. At the top of the cam shaft, there is provided a handle 208 for pressing the plug 201 against the inside of the receptacle 202 and at the same time, rotating the cam shaft 207.
Moreover, the housing 203 is provided with a spring support section 209 for actuating the cam shaft 207 upward, and a spring 220. The cam shaft 207 has a ringed brim projecting from its side which presses against the spring 220.
The receptacle 202 has a receptacle housing 209. In the lower part of the housing 209, a receptacle board 210 is provided. On the top surface of the receptacle board 210, a plurality of contact pads 211 (or contact strips) to be pressed against the contact pads 206 of the plug are formed. On the bottom surface of the receptacle board 210, a plurality of electrode sections 213 are formed which are internally connected to the contact pads 211 and electrically connected to the printed wiring board 212 of the other electronic apparatus.
The receptacle 202 further has a stiffener 214 serving as a support member in its lower part. The printed wiring board 212 of the other electronic apparatus is inserted between the stiffener 214 and the bottom surface 215 of the receptacle housing 209 and then screwed there (not shown), thereby fixing the receptacle 202 to the circuit board 212. The receptacle 202 is provided with a set of folding doors 222 on both sides. When the plug 201 is not inserted, the doors 222 are turned horizontally to close the receptacle 202.
To connect the plug 201 and the receptacle 202, the plug 201 is inserted into the receptacle 202 in such a manner that the doors 222 are forced open left and right and the cam shaft 207 is further pressed downward, opposing the actuation of the spring 220. Then, the cam shaft 207 is rotated with the handle 208, thereby pulling a projecting part 216 sticking out of the cam shaft 207 under the locking surface 218 of the central concave part 217 of the bottom surface of the stiffener 214. As a result, the elastic force of the spring 220 makes an electrical connection between the individual contact pads 206, 211 of the plug and receptacle. To remove the plug 201, the cam shaft 207 is pressed downward, opposing the actuating force of the spring 220, and then is rotated in the opposite direction, thereby unlocking the projecting part 216.
In the conventional multicore connector 100 of FIG. 11, turning the handle causes the contacts to move in the lateral direction by means of the cam mechanism near the center, which assures the operation capability with a ZIF (zero insertion force) structure. Since the contact pins 107, 109 are deformed elastically to make contact with one another, as the number of cores increases, the rotational torque of the cam shaft 104 becomes larger at the time of engagement, which is a problem. Furthermore, since spring actions are needed, this lengthens the signal line, making interference, such as crosstalk, liable to take place in the transmission characteristic of the electric signals, which tends to have an adverse effect on the transmission of high-speed signals.
Furthermore, in a conventional multicore connector 200 of FIG. 12, since no contact pin is used, the signal lines in the longitudinal direction become shorter, enabling the height of the connectors in the longitudinal direction to be reduced. However, to increase the rigidity of the connector 200 and connect the connector 200 to the circuit board 212 on which the connector 200 is to be mounted, a stiffener 214 to fix the connector 200 to the board 212 has to be provided on the back of the board 212. Furthermore, an opening 223 has to be made in the board. As a result, the connector 200 is made larger on the whole and the parts mounting area is made smaller, which is a problem. In addition, there is another problem: even if the plug housing 203 and receptacle housing 209 are made of a metal, it is difficult to make electrical connection to cause them to be grounded completely.
An object of the present invention is to provide a multicore connector which makes the rotational torque of the cam shaft smaller and shortens the signal lines to improve the EMI characteristic, or the transmission characteristic of electric signals, and prevent interference, such as crosstalk, and which is suitable for the transmission of high-speed signals. Another object of the present invention is to provide a multicore connector which reduces the number of parts to be mounted on an electronic apparatus, makes the parts mounting area smaller by downsizing the whole connector, and enables the plug housing and receptacle housing to be grounded completely.